API Calcium Test

jlmawp

jlmawp

New member
So the last time I measured Calc was probably 6 weeks ago. All was fine, was at about 420. I went to test after a cleaning today, and am showing only at 260. I did the test a second time, double-checking the directions just to be sure...again, 260.

I have a 9-gallon nano, and I only use Reef Crystals. I dose with B-Ionic 2-step after every weekly water change. I have one SPS, and 5 LPS (all fairly small) in tank. Is it possible that they are really eating up that much calcium, or is my API test bad? The expiration isn't for another 18 months.

Just wanted to get a couple expert opinions before I spend more money on tests.
 
Do you have a reading for alk or Mg? It's possible that the Ca is precipitating. With weekly water changes, I don't think that much Ca would be consumed.
 
You cannot read the API test results to the accuracy that you can the Salifert or Red Sea Pro series, but it should get you in the ballpark, so I would assume that your test results are at least close to being correct. One thing that does jump out at me is that you are dosing two part right after making a water change with a salt that is already high in calcium and alkalinity. Doing that you are likely to have a fair amount of calcium precipitation since the new saltwater is already close to the precipitation point, you would be better off waiting until mid-way between water changes to dose the two part. That way your water parameters would stay closer to the desired parameters rather than having a big spike at water change time and then seeing the levels slowly drop during the week. If you have a lot of coraline algae it will consume a lot of alkalinity and calcium. The most important thing for you to check is your magnesium level, if it is low it will be impossible to keep your alkalinity and calcium levels at the proper levels.
 
Agreed

Mag should be 3 x the normal cal parameter.

I use the Red Sea Pro kits for the big 3 but API is good for a quick ballpark calcium #.
 
Cross test your water with LFS (I think your test is fine). If your CA is low, then test Mg.

If your Mg is low, your problem comes from low Mg. Bring your Mg up, the Ca will be better
 
Thank you for your replies. I'll head to the LFS with a water sample and probably kick up an MG test while I'm at it. Appreciate the advice.

Since I've been in this for about a year now, maybe it's time I get myself some more reliable tests.
 
There is nothing wrong with API test kits for CA and alk. I use them all the time. Once in a great while I get a wild result and then do a test with my Salifert test kit for Ca and alk. Almost every time the Salifert kit gives me a result that just mirrors the API result.

And just because the other test kits offer readings in a 'finer' scale than the API kits do, that doesn't make them more accurate. Example: Two clocks, an API clock and a Salifert clock both tell you the time. The API clock only has hands for hours and minutes, not seconds. The Salifert clock has hands for hours, minutes and seconds. The API clock says it's 1:15pm and the Salifert clock says it's 1:12:07pm. Which one is right? The Salifert clock appears to be more 'accurate' just because it has finer gradations, but that isn't the same thing as being right. What if the real time was 1:16.11pm? A finer scale is NOT the same thing as being more accurate!

To the OP, I'd take a water sample and your test kit to an LFS, or better, a friend who is also a reefer and test your water and his water with your API kit and whatever kit he uses.

And why are you dosing 2 part when you do water changes? Do your water change and test the water. Then do dosing if needed. Test again before the next water change and see how much (or how little) change there is. It's a small tank so parameters could change quickly, but I think something else is going on in your tank.
 
Last edited:
Ron Reefman said:
There is nothing wrong with API test kits for CA and alk. I use them all the time. Once in a great while I get a wild result and then do a test with my Salifert test kit for Ca and alk. Almost every time the Salifert kit gives me a result that just mirrors the API result.

And just because the other test kits offer readings in a 'finer' scale than the API kits do, that doesn't make them more accurate.
Click to expand...

Yes, and you can always double the volume of the API test. This would give 10ppm increments instead of 20ppm for the Ca test, and 0.5 dKH increments instead of 1.0 dKH for alk.
 
Ron Reefman said:
To the OP, I'd take a water sample and your test kit to an LFS, or better, a friend who is also a reefer and test your water and his water with your API

And why are you dosing 2 part when you do water changes? Do your water change and test the water. Then do dosing if needed. Test again before the next water change and see how much (or how little) change there is. It's a small tank so parameters could change quickly, but I think something else is going on in your tank.
Click to expand...

I'm dosing 2-part after water changes because I tested meticulously for a few months, and found the right amount to add every week to boost calc a bit above the Reef Crystal baseline. It's a very minimal amount...about 2ml of each. I struck a nice balance and got a little over-confident about the levels over time,which resulted in not testing for a good while. Lesson learned there. I have a lot of coralline for how small my tank is, which I forgot to mention up above. Before dosing, my levels were at 389-400 when I tested, depending on how Recently I did a WC.

Thanks for the clarity on the API test. The rest of my tests are also made by them, so it's good to hear they are at least decent.

I've been pretty sick with the flu the last few days, and am going out of town this weekend for the holiday, but when I get back, I'll hit up the LFS and come back to you all with the results.
 
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And just because the other test kits offer readings in a 'finer' scale than the API kits do, that doesn't make them more accurate. Example: Two clocks, an API clock and a Salifert clock both tell you the time. The API clock only has hands for hours and minutes, not seconds. The Salifert clock has hands for hours, minutes and seconds. The API clock says it's 1:15pm and the Salifert clock says it's 1:12:07pm. Which one is right? The Salifert clock appears to be more 'accurate' just because it has finer gradations, but that isn't the same thing as being right. What if the real time was 1:16.11pm? A finer scale is NOT the same thing as being more accurate!

Amen. The API reads close enough and can be done in seconds as opposed to breaking out a chemistry set. If the test is a pita to do then you won't do it. Levels can change hour by hour and it's irrelevant whether it's 420 or 435. I just want to be in the ballpark and be relatively stable. Your level still seems awfully low from just low Mg level and without seeing signs of obvious Ca snow/precipitation.
 
Ron Reefman said:
There is nothing wrong with API test kits for CA and alk. I use them all the time. Once in a great while I get a wild result and then do a test with my Salifert test kit for Ca and alk. Almost every time the Salifert kit gives me a result that just mirrors the API result.

And just because the other test kits offer readings in a 'finer' scale than the API kits do, that doesn't make them more accurate. Example: Two clocks, an API clock and a Salifert clock both tell you the time. The API clock only has hands for hours and minutes, not seconds. The Salifert clock has hands for hours, minutes and seconds. The API clock says it's 1:15pm and the Salifert clock says it's 1:12:07pm. Which one is right? The Salifert clock appears to be more 'accurate' just because it has finer gradations, but that isn't the same thing as being right. What if the real time was 1:16.11pm? A finer scale is NOT the same thing as being more accurate!

To the OP, I'd take a water sample and your test kit to an LFS, or better, a friend who is also a reefer and test your water and his water with your API kit and whatever kit he uses.

And why are you dosing 2 part when you do water changes? Do your water change and test the water. Then do dosing if needed. Test again before the next water change and see how much (or how little) change there is. It's a small tank so parameters could change quickly, but I think something else is going on in your tank.
Click to expand...

dendrite said:
And just because the other test kits offer readings in a 'finer' scale than the API kits do, that doesn't make them more accurate. Example: Two clocks, an API clock and a Salifert clock both tell you the time. The API clock only has hands for hours and minutes, not seconds. The Salifert clock has hands for hours, minutes and seconds. The API clock says it's 1:15pm and the Salifert clock says it's 1:12:07pm. Which one is right? The Salifert clock appears to be more 'accurate' just because it has finer gradations, but that isn't the same thing as being right. What if the real time was 1:16.11pm? A finer scale is NOT the same thing as being more accurate!

Amen. The API reads close enough and can be done in seconds as opposed to breaking out a chemistry set. If the test is a pita to do then you won't do it. Levels can change hour by hour and it's irrelevant whether it's 420 or 435. I just want to be in the ballpark and be relatively stable. Your level still seems awfully low from just low Mg level and without seeing signs of obvious Ca snow/precipitation.
Click to expand...
:beer:

I have seen many reviews on test kit comparisons... all the conclusions the same...
Some people think if your not spending the most amount of money you can on something your not getting your money worth.. I agree thou some test do give bigger result range.. but is it really needed... People were keeping perfectly stable reef tanks before water testing was even available...
 
To all that have opinions on test kit accuracy:

Our local club did a test of a wide variety of test kits and test kit users (our members) on a single sample of water that was then tested by a big name test outfit. The results? All over the board. Even people using the same brand of test kits were getting very different results. And the API kits were just as in the ballpark as Salifert, Red Sea and others. My personal opinion is that the person doing the test has as much or more to do with variations in results as the brand of test kit.

Conclusions:
Don't take test results too seriously, you are looking for consistency in how you do the test itself as well as in the results you get. The difference between a Ca of 400 and 450 just isn't that big a deal. Alk is the only one I take seriously, so I keep mine a up at 8dkh and I'd rather be higher than lower.
 
I used to be a test junkie and have tried them all. In the end, I use api test kits for alk, ca and nitrate only for at least the past 3 years. If I ever get a reading that looks off, I just test again.
 
So I'm bumping this thread after going to the LFS. My params tested at 260 for Calcium (same as home), so I guess my test isn't "bad", but I'm still having a hard time believing this level with regular water changes.

The guy at the store asked what I used for salt, and when he found out it was Reef Crystals, he told me that they recently changed their product and he has noticed a drop in the amount of some levels, particularly Calcium. Can anyone else confirm this?

Even still, a drop that far? Seems crazy to me.

I'm going to order Mag and alk tests (I should have weeks ago, but holiday nuttiness) to see if something is way off. From what a couple people in this thread are saying, low mag can make calcium appear very low. Guess I should have asked that they test mag/alk, but it slipped my mind somehow.

Cal can't be THAT low though, since I'm seeing growth in all of my LPS and my one SPS frag.
 
jlmawp said:
So I'm bumping this thread after going to the LFS. My params tested at 260 for Calcium (same as home), so I guess my test isn't "bad", but I'm still having a hard time believing this level with regular water changes.

The guy at the store asked what I used for salt, and when he found out it was Reef Crystals, he told me that they recently changed their product and he has noticed a drop in the amount of some levels, particularly Calcium. Can anyone else confirm this?

Even still, a drop that far? Seems crazy to me.

I'm going to order Mag and alk tests (I should have weeks ago, but holiday nuttiness) to see if something is way off. From what a couple people in this thread are saying, low mag can make calcium appear very low. Guess I should have asked that they test mag/alk, but it slipped my mind somehow.

Cal can't be THAT low though, since I'm seeing growth in all of my LPS and my one SPS frag.
Click to expand...

Not true.
 
My guess is that you precipitated calcium at some point.

I also use API for calc, alk, and pH. I test some newly mixed water (after several hours of mixing) with every new batch of salt. Yes, RC is lower than advertised for Ca and Mg, but not that low. Usually Ca is round 400 and MG in the 1200 range. I have contacted them about this and was told to use 3 different test kits to confirm, that my container could be leaching (absorbing Ca and MG??), and some other bogus excuse. I use turbo calc (calcium chloride) and Tech M to bring my change water up before adding it to the tank. Same thing you are doing with dosing after a water change, I just mix it into the change water so it is mixed before going into the tank at a higher concentration. I feel I am less liely to get precipitation this way. I don't know that it makes a difference.

Kim
 
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